Not applicable.
Not applicable.
The present invention relates to a wellhead production pumping tree and to providing in it one or more access ports for accommodating connection assemblies for electrical heating and instrumentation strings.
It is common today to produce heavy oil from reservoirs formed of unconsolidated sands. This type of production is often associated with problems or issues such as:
wax formation clogging the upper end of the tubing string;
injection of steam into the reservoir to heat the oil, which often makes it desirable to monitor reservoir conditions, such as temperature and pressure, from the production wells; and
the use of down hole progressive cavity pumps for moving the heavy oil to surfacexe2x80x94these pumps are driven by rotating rod strings powered by motor and drive assemblies mounted on top of the pumping tree. These assemblies vibrate and apply stresses to the pumping tree that can cause it to part, particularly at threaded connections.
The oil industry has developed solutions to these problems in various ways, including:
using an electrical heating cable or string, in contact with the upper end of the production tubing, to apply heat to the oil passing there through to reduce the formation of wax;
running a small diameter string of tubing into the production casing bore to circulate out sand; and
running or permanently providing an instrumentation string, typically a cable with attached sensors, in the production casing bore when measurements are to be taken.
These xe2x80x98stringsxe2x80x99 are referred to herein as xe2x80x98supplemental stringsxe2x80x99.
A pumping tree is an assembly mounted to the upper end of a wellhead tubing head. For many years it consisted of a stack of separate components threaded together and forming a central vertical bore extending there through, the components being:
an adapter comprising a bottom flange, for bolting to the tubing head flange, narrowing down to a threaded top connection of smaller diameter;
a production blow-out preventer (xe2x80x9cB.O.P.xe2x80x9d) having a body forming opposed horizontal openings, in which are located the ram components, and having bottom and top threaded connections; and
a flow tee body forming a horizontal side outlet and having top and bottom threaded connections.
More recently the housing of the production pumping tree has been cast or forged as a single integral unit. As a result, the threaded connections have been eliminated and the tree has only top and bottom connections, which are typically flanged or studded. The height of the unit is reduced and the side walls are thicker. This product, disclosed in Canadian Patent No. 2,197,584, issued to the present applicants, has alleviated the parting problem arising from mounting the high r.p.m., heavy, vibrating, off-center rod rotating drive assembly on the tree.
In broad form, the present invention is directed to an integral production pumping tree whose housing forms a vertical production tubing bore and openings for receiving a well head flow control component such as a horizontal blow-out preventer (B.O.P) valve and flow tee openings, all located off-center in one side section of the housing, and at least one off-center vertical access bore formed in the other side section.
The word xe2x80x98off-centerxe2x80x99 is intended to indicate that the production tubing bore axis and the access bore axis are each spaced laterally or offset from the central axis of the pumping tree.
The pumping tree is preferably combined with a tubing hanger, to be used in the wellhead tubing head, which also forms vertical off-center bores corresponding or coinciding with those of the pumping tree.
A detailed and preferred embodiment of the invention comprises:
a production pumping tree having an integral housing having first and second sections;
the housing forming an off-center vertical production tubing bore and off-center horizontal B.O.P. and flow tee openings in the first section and at least one off-center vertical access bore in the second section; and
an upper portion of the second section more preferably being partly or entirely cut-away, to provide space for connecting a supplemental string to extend through an access bore.
Broadly stated, the invention is directed to a production pumping tree for use in a wellhead, comprising: a housing formed from a single piece of steel and having first and second sections; the first housing section forming an off-center vertical production tubing bore connected with horizontal blow-out preventer component openings and a horizontal flow tee opening; the second housing section forming at least one access bore for enabling access through the housing for a supplemental string.